Large animal models of cardiovascular disease

The human cardiovascular system is a complex arrangement of specialized structures with distinct functions. The molecular landscape, including the genome, transcriptome and proteome, is pivotal to the biological complexity of both normal and abnormal mammalian processes. Despite our advancing knowledge and understanding of cardiovascular disease (CVD) through the principal use of rodent models, this continues to be an increasing issue in today's world. For instance, as the ageing population increases, so does the incidence of heart valve dysfunction. This may be because of changes in molecular composition and structure of the extracellular matrix, or from the pathological process of vascular calcification in which bone-formation related factors cause ectopic mineralization. However, significant differences between mice and men exist in terms of cardiovascular anatomy, physiology and pathology. In contrast, large animal models can show considerably greater similarity to humans. Furthermore, precise and efficient genome editing techniques enable the generation of tailored models for translational research. These novel systems provide a huge potential for large animal models to investigate the regulatory factors and molecular pathways that contribute to CVD in vivo. In turn, this will help bridge the gap between basic science and clinical applications by facilitating the refinement of therapies for cardiovascular disease.

Insulin-like growth factor binding proteins initiate cell death and extracellular matrix remodeling in the mammary gland

We have demonstrated that insulin-like growth factor binding protein-5 (IGFBP-5) production by mammary epithelial cells increases dramatically during forced involution of the mammary gland in rats, mice and pigs. We proposed that growth hormone (GH) increases the survival factor IGF-I, whilst prolactin (PRL) enhances the effects of GH by decreasing the concentration of IGFBP-5, which would otherwise inhibit the actions of IGFs. To demonstrate a causal relationship between IGFBP-5 and cell death, we created transgenic mice expressing IGFBP-5, specifically, in the mammary gland. DNA content in the mammary glands of transgenic mice was decreased as early as day 10 of pregnancy. Mammary cell number and milk synthesis were both decreased by approximately 50% during the first 10 days of lactation. The concentrations of the pro-apoptotic molecule caspase-3 was increased in transgenic animals whilst the concentrations of two pro-survival molecules Bcl-2 and Bcl-x were both decreased. In order to examine whether IGFBP-5 acts by inhibiting the survival effect of IGF-I, we examined IGF receptor- and Akt-phoshorylation and showed that both were inhibited. These studies also indicated that the effects of IGFBP-5 could be mediated in part by IGF-independent effects involving potential interactions with components of the extracellular matrix involved in tissue remodeling, such as components of the plasminogen system, and the matrix metallo-proteinases (MMPs). Mammary development was normalised in transgenic mice by R3-IGF-I, an analogue of IGF-I which binds weakly to IGFBPs, although milk production was only partially restored. In contrast, treatment with prolactin was able to inhibit early involutionary processes in normal mice but was unable to prevent this in mice over-expressing IGFBP-5, although it was able to inhibit activation of MMPs. Thus, IGFBP-5 can simultaneously inhibit IGF action and activate the plasminogen system thereby coordinating cell death and tissue remodeling processes. The ability to separate these properties, using mutant IGFBPs, is currently under investigation.

Dolly for dinner? Assessing commercial and regulatory trends in cloned livestock

As cloning technologies become more widely established, will products enter the food chain sooner than regulatory agencies and the public might be prepared for?

Prolactin inhibits cell loss and decreases matrix metalloproteinase expression in the involuting mouse mammary gland but fails to prevent cell loss in the mammary glands of mice expressing IGFBP-5 as a mammary transgene

Insulin-like growth factor-binding protein 5 (IGFBP-5) mediates involution of the mammary gland. The decrease in DNA content and mammary gland weight which accompanies involution was inhibited by prolactin (PRL) in wild-type but not transgenic mice expressing IGFBP-5. Phospho-STAT5 protein levels were significantly lower in IGFBP-5 transgenic mice during lactation suggesting that IGFBP-5 antagonises PRL signalling in the mammary epithelium. In contrast, phospho-STAT3 levels increased during involution to a similar extent in both wild-type and transgenic mice and were unaffected by PRL. PRL inhibited gene expression of matrix metalloproteinases (MMPs) 3 and 12 but not tissue plasminogen activator or plasmin in wild-type and transgenic animals. The effects of PRL on MMPs appear to be indirect since PRL failed to inhibit MMP-3, -7 or -12 expression in HC-11 cells or in a co-transfection including an activated PRL receptor, STAT5 and a MMP-3-luciferase reporter gene. PRL is a potent inhibitor, both of cell death, an effect which is suppressed by IGFBP-5, and of MMP expression, which is independent of the actions of IGFBP-5.

CMV enhancer-promoter is preferentially active in exocrine cells in vivo

The CMV enhancer-promoter sequence is often used as a transcriptional regulatory element in vector systems. We have used this control element to drive expression of GFP in a lentivirus vector transgene in pigs and chickens. Promoted as a 'universal' enhancer/promoter element capable of transcriptional activity in a number of cells in vitro, CMV-GFP transgene expression in vivo is preferentially observed in exocrine cells. This expression profile validates the use of this transcriptional control sequence to target expression to exocrine cells in gene transfer strategies.

Gene-Edited Meat: Disentangling Consumers' Attitudes and Potential Purchase Behavior

Novel gene-editing (GE) technologies provide promising opportunities to increase livestock productivity and to tackle several global livestock production sustainability and food security challenges. However, these technologies, as with previous genetic modification technologies in food production, are very likely to generate social controversy and opposition toward their use in the meat industry. Here, we explored public attitudes and consumption predisposition toward gene-edited meat products and their potential added benefits to livestock farming. Our results show that societal perception currently comes as a package, where the use of gene-editing technology acts as an extrinsic cue of meat products quality, and is used to make a range of inferences about all quality facets at once. Although consumers with anti-GE attitudinal positions generally were not sensitive to price discounts or added benefits, added benefits increased the consumption predisposition of most moderate and pro-GE consumers, where benefits related to animal welfare had larger effects than those relating to the environment or human health issues.

337 NONMEIOTIC INTROGRESSION OF QUANTITATIVE TRAIT NUCLEOTIDES AND CORRECTION OF CONGENITAL MUTATIONS IN LIVESTOCK WITH TRANSCRIPTION ACTIVATOR-LIKE EFFECTOR NUCLEASES

Genetic enhancement of livestock productivity and welfare are major goals of breeding and genetics programs. However, the introgression of desirable alleles across breeds is slow and inaccurate. The development of gene editing technologies would provide the opportunity to accelerate the genetic improvement of a diversity of livestock breeds. Transcription activator-like effector nucleases (TALEN) are programmable nucleases that join the modular DNA binding domain of transcription activator-like (TAL) effectors with FokI endonuclease. We found that TALEN could be easily manufactured and that 64% displayed activity in swine and cattle primary fibroblasts, with cleavage of 1.5 to 45% of chromosomes in cell populations, as measured by Surveyor assay. Clonal isolation and sequencing revealed that up to 84% of cells contained at least one modified allele, with up to 24% of cells containing biallelic or homozygous chromosomal modification. Co-transfection of a customized TALEN pair with a template containing a specific allele was effective at the nonmeiotic introgression of quantitative trait into naïve cattle breeds. We will also describe the repair of 2 recently described embryonic lethal mutations that are segregating in important dairy cattle breeds (JH1 and HH1). Injection of TALEN mRNA into the cytoplasm of pig and cattle zygotes was capable of inducing gene knockout (KO) in 27 to 75% of embryos analysed (n = 4–59), nearly half of which (8/19) harbored biallelic modification. We will present data describing efforts towards gene conversion by direct injection of livestock embryos. Finally, we will present alternative strategies for the incorporation of gene editing in livestock production systems by cloning or embryo treatment.

Disease-resistant genetically modified animals

Infectious disease adversely affects livestock production and animal welfare, and has impacts upon both human health and public perception of livestock production. The authors argue that the combination of new methodology that enables the efficient production of genetically-modified (GM) animals with exciting new tools to alter gene activity makes the applications of transgenic animals for the benefit of animal (and human health) increasingly likely. This is illustrated through descriptions of specific examples. This technology is likely to have specific application where genetic variation does not exist in a given population or species and where novel genetic improvements can be engineered. These engineered animals would provide valuable models with which to investigate disease progression and evaluate this approach to controlling the disease. The authors propose that the use of GM animals will complement the more traditional tactics to combat disease, and will provide novel intervention strategies that are not possible through the established approaches.

95 PRODUCTION OF GENE-EDITED PIGS, CATTLE, AND LAMBS BY EMBRYO INJECTION OF TALENS OR ZFNs

Transcription activator-like effector nuclease (TALEN) and zinc finger nuclease (ZFN) DNA editing technology enables site-directed engineering of the genome. To date, all gene-edited large animals have been produced by treatment of somatic cells and cloning to produce gene-edited offspring. Although effective, it does not take advantage of the ‘leave-no-trace' aspect of site-specific nucleases, and the derivation of food animals by cloning is negatively perceived by the public. Thus, we have investigated production of gene-edited pigs, cattle and sheep by direct injection of TALEN or ZFN mRNAs to develop loss-of-function alleles for disease resistance (RELA) or enhanced meat production (GDF8). In vitro studies demonstrated activity of TALENs by cytoplasmic injection of mRNAs from dosages of 2 to 20 ng mL–1 with an apparent increase in both editing frequency and toxicity at high dosage. Our first pregnancies were produced by transfer of pig embryos (in vivo produced) injected with 2 ng mL–1 RELA TALEN mRNA. Pregnancy was confirmed in 5 of 7 recipients 4 of which went full term giving rise to 39 piglets, 8 of which carried editing events (21%). In parallel, we injected ZFN mRNA (2 ng mL–1) targeted to a similar site of the RELA gene and 2 of 2 recipients became pregnant, resulting in the birth of 9 piglets, one of which was edited (11%). For cattle injections, we derived zygotes by ovum pickup from selected Nelore dams followed by in vitro maturation and fertilization with Nelore semen. Low (2 ng mL–1) and medium (5 ng mL–1) dosages of GDF8-targeted TALENs resulted in Day 7 development to morula/blastocyst stage in 40% (n = 18) and 10% (n = 66) of cultured embryos, respectively. A total of 20 morula/blastocysts were chosen for transfer to 11 recipients, resulting in two full-term pregnancies. One pregnancy produced two calves, both of which carried edited GDF8 alleles. Complications with parturition of the second pregnancy resulted in 2 stillborn calves, the genotypes of which are under investigation. Finally, 2 ng mL–1 of TALEN mRNA targeted to ovine GDF8 was injected into in vivo-produced sheep zygotes and transferred into nine recipients, 3 blastocysts each. The pregnancy rate, number of live-born animals, and gene editing frequency is under investigation and will be reported.

On the use of post-transcriptional processing elements in transgenes

RNA processing events modulate final productivity of a given transgene. We have evaluated a series of RNA elements for their ability to enhance α1-antitrypsin production in mammary cells. Our results indicate the need for a case-by-case assessment of each construct design and the occurrence of gene silencing events in vivo.